Practice question
Question
A steel wire of length 2.7m and cross-sectional area 2×10−6m2 is stretched by 0.54mm. If the Young's modulus of steel is 2×1011N/m2, what is the stress?
Explanation
Strain: Strain = ΔLL = 0.54×10−32.7 = 2×10−4. Young's modulus: Y = StressStrain. Stress: Stress = Y×Strain = 2×1011×2×10−4 = 4×107N/m2. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 4×107N/m2. This satisfies dimensional consistency and physical conditions given, so option C is scientifically correct.